TABLE 2.

Sporulation of B. subtilis strains grown in modified TF mediuma

StrainTime (h)Total no. of viable cells (CFU/ml)No. of heat- resistant spores (CFU/ml)bFrequency of sporulation (%)
61884 (rel+)126.0 × 1082.5 × 1040.004
181.7 × 1082.8 × 1040.016
242.0 × 1081.6 × 1060.8
366.8 × 1084.2 × 1076
61883 (relA1)125.6 × 1082.1 × 1050.04
183.2 × 1083.7 × 1050.1
247.3 × 1087.2 × 1050.1
367.3 × 1087.0 × 1050.1
TI71 (relA1 ΔcodY)123.1 × 1081.8 × 102<0.001
186.7 × 1081.0 × 1071
247.8 × 1086.4 × 1078
365.4 × 1081.7 × 10831
  • a TF medium (see Materials and Methods) was supplemented with 1 mM Ca(NO3)2·4H2O, 0.1 mM MnCl2·4H2O, and 1 μM FeSO4·7H2O.

  • b Heat-resistant spores were determined using L agar plate after heating the cultured broth at 80°C for 15 min.